Cathode ray tube circuit



Oct. 22, 1940. H. RlNlA CATHODE RAY TUBE CIRCUIT Filed March 18, 1939 //v II/ENTOR HERRE RIN/A I A TTORNE Y Grin 70.4%,:

Patented a. 22, 1940 I arrayed fcA'i HonEnAY runncmcprr I Her're :RihiadEindhfien, Netherlands, assignor, j I by mcsne assignments, to Radio Corporation of I America,

Delaware New York, N. Y-.', a corporation of Api lication Marchlii, 1939'; Serial mam-15 f y InGermanyMamh-a 8.

40mins. (cl. 250 .2r)

This inven-tion concerns a circuit arrangement comprising a cathode-ray tube having a control electrode to which is supplied an alternating voltage, such as is used in television'receivers and furthermore the slope of the characteristic curve I is generally small. (Fig.1) Owing to this small removed by-supplying the control voltage at the slope it is not possible, by means of a degenerative back-coupling, such asis known from the amplication practice, to linearisethe shape of the characteristic curve since for the obtainment of asuflicient degenerative back-coupling even a small mutual conductancerequiresthe insertion of a very large impedance in the cathode lead of the cathode-ray tube. The self-capacity of this impedance preponderates in this case particularly I at high frequencies of the control voltage, due to which substantially no back-coupling is ob tained for these frequencies.

According to the invention this difficulty is same time tothe input circuit of a discharge tube in which the slope of the grid voltage/anode cur- .rent characteristic is greaterthan that of the cathode-ray tube and in which a voltageis derived from the anode circuit of the discharge tube which is supplied in phase-opposition to the control voltage of the control electrode of the cathode-ray tube. I I I I In describing the invention in detail, reference will be made to the drawing in which Fig. 1

' shows the control voltage anode current characteristic. of a cathode ray tube diagrammatically; I f

Fig. 2 shows in graphical form the grid voltage anode current characteristic a thermionic tube,

while Fig. 3 shows one embodiment of the invention inwhich a thermionic tube is connected in par-' .allel with the cathode and control electrode of.

the'cathode ray tube. l

Preferably a discharge tube is used whose conb trol grid voltage/anode current characteristic has a shape similar to that of the control voltage/anode current characteristic of the cathode ray tube (Fig. 2).

The invention will be more clearly understood by reference to Fig.3 'of the accompanying drawing representing, by waykof example, one formof construction thereof. I

Fig. 3 shows a cathode-raytube I comprising a cathode 2, a control grid 3, a first anode 4, and

an anode 5 which may, for instance, be coated with fluorescent materiaL' To the control electrode 3 is connectedthe control grid 6 of thedischarge tube 1 whose cathode 8 is connected to the cathode 2 of the cathode-ray tube. Therequired anode-voltages for the tubes l and 1 are,

delivered bya supply .9.

The common cathode lead for the two tubes I and 1 includes a resistance H). The control voltage E for the cathode-raytube is applied bei tween thecontrol electrode 3 and the end of the resistance l!) remote from the cathodes Zand 8.

To improve the characteristic curve of the cathode-ray tube'it is necessary that a suflicient voltage is set up at the resistance I0, which voltage is supplied to the grid 3 in phase-opposition to the control voltage-E. The voltage set upat the resistance I0 is substantially caused by the anode current of the tube 1- whose mutual con ductance is greaterthanthat of the cathode-ray tube. Consequently the resistance [0 may be I much smaller than in the absence of the tube I. The self-capacity of the resistance In may now I also be neglected at high frequencies of the'conetrol voltage, thus obtaining a degenerative back- 1 coupling which is independent of the frequency.

If it is desired that the degenerative backcoupling should depend in a definite manner on the frequency the resistance l0 may bereplaced by a suitable impedance. I I

Furthermore, it will be appreciated that suitable networks may be included in the connecting leads H and I2 between the control electrode '3 and the control grid 6, and the cathode v2 and 6 respectively, which networks may involve again a frequency-dependent degenerative back-coupling.

The form of construction described above includes a so-called negative current feed back by means of a resistance in the common cathode same result can be obtained by means of a socalled negative voltage feed back in which the anode circuit of the discharge tube 1 comprises animpedance and the voltage set up across a part of this impedance is supplied to the cathoderay tube in phase-opposition to the control voltage of the control electrode 3. I

Furthermore the drawing shows a cathode-ray lead. It will be appreciated, however,that the tube without a deflecting system; it will be understood, however, thatany desired system maybe used.

I ing a cathode ray tube having a cathode, a control electrode, an anode, and a target electrode,

15 I means to 'supply'control voltage to said control a :the control electrode and cathode, simultaneous- 1y deriving a voltage from the supplied control voltage, and supplying the derived voltage between said control electrode and cathode in antiphase relationship to the supplied control voltage. 2. A cathode ray tube control system compris electrode and to said cathode through a series resistance, a thermionic tube having, a cathode, a grid and anode, connections from the control electrode to the grid and from the cathode of said cathode ray tube to the cathode of said therminput circuit in anti-phase relation ionic tube, and a voltage supply for supplying both of said anodes and said target electrode.

3. A cathode ray tube system comprising a cathoderay tube having an input circuit including a resistance, means to supply control voltage to said input circuit, thermionic means for deriving avoltage from said control voltage and connections from said thermionic means to said resistance to supply the derived voltage to said input circuit in anti-phase relation to the supplied control voltage.

4. A cathode ray tube system comprising a cathode ray tube having an input circuit including an impedance, means to supply control voltage to said input circuit, thermionic means for deriving a voltage from said control voltage, and

connections from said thermionic means to said resistance to supply the derived voltage to said to the supplied control voltage.

I-IERRE RINIA. 

